Ventilators help patients to breath by mechanically pumping and exhausting air from the lungs. Ventilators may be used to replace or supplement the patient's muscular effort normally used to inflate and deflate the lungs.
Ventilators may function to supply a patient with a supply of clean breathable gas (usually air, with or without supplemental oxygen) at a therapeutic pressure or pressures, at appropriate times during the subject's breathing cycle. Pressure changes may be implemented in a synchronized fashion so as to permit greater pressures during inspiration and lower pressures during expiration. Therapeutic pressure is also known as the ventilation pressure.
Ventilators typically include a flow generator, an inlet filter, a mask, an air delivery conduit connecting the flow generator to the mask, various sensors and a microprocessor-based controller. Optionally, in lieu of a mask, a tracheotomy tube may also serve as a patient interface. The flow generator may include a servo-controlled motor, volute and an impeller that forms a blower. In some cases a brake for the motor may be implemented to more rapidly reduce the speed of the blower so as to overcome the inertia of the motor and impeller. The braking can permit the blower to more rapidly achieve a lower pressure condition in time for synchronization with expiration despite the inertia. In some cases the flow generator may also include a valve capable of discharging generated air to atmosphere as a means for altering the pressure delivered to the patient as an alternative to motor speed control. The sensors measure, amongst other things, motor speed, mass flow rate and outlet pressure, such as with a pressure transducer or the like. The apparatus may optionally include a humidifier and/or heater elements in the path of the air delivery circuit. The controller may include data storage capacity with or without integrated data retrieval and display functions.
Ventilators also control the timing and pressure of breaths pumped into the patient and monitor the breaths taken by the patient. The methods of control and monitoring patients typically include volume-cycled and pressure-cycled methods. The volume-cycled methods may include among others, Pressure-Regulated Volume Control (PRVC), Volume Ventilation (VV), and Volume Controlled Continuous Mandatory Ventilation (VC-CMV) techniques. The pressure-cycled methods may involve, among others, Assist Control (AC), Synchronized Intermittent Mandatory Ventilation (SIMV), Controlled Mechanical Ventilation (CMV), Pressure Support Ventilation (PSV), Continuous Positive Airway Pressure (CPAP), or Positive End Expiratory Pressure (PEEP) techniques.
Ventilators provide breathing assistance to patient suffering from diseases affecting the musculature required for breathing, such as muscular dystrophies, polio, amyotrophic lateral sclerosis (ALS), and Guillain-Barre syndrome. Ventilators may be used to treat conditions such as respiratory insufficiency or failure due to lung, neuromuscular or musculoskeletal disease and diseases of respiratory control. They may also be used for conditions related to sleep disordered breathing (SDB) (including mild obstructive sleep apnea (OSA)), allergy induced upper airway obstruction or early viral infection of the upper airway. Ventilators are also used to provide breathing assistance to sedated patients undergoing surgery or for patients suffering severe injuries, such as high spinal cord injuries and head traumas. In addition, a ventilator may also be configured to expand non-functioning regions of a patient's lung(s), such as collapsed alveoli.
Ventilators conventionally are mechanically complex devices which require highly trained persons to service and repair. Within the housing of a ventilator are a number of various tubes to connect mechanical and electrical valves and sensors used to control and measure the characteristics of ventilation. The tubes are typically individually connected to various ports and devices in the housing of the ventilator.